A green replacement route to produce phosphatidylserine in environmentally friendly edible oil-water systems and investigations on the enzymatic mechanism.

Phosphatidylserine (PS) has many applications in functional food and pharmaceutical industries because of its critical role in activating important signal transduction pathways and modulating neurotransmitter release and receptor function. Several edible oils have been used to construct oil-water systems for the efficient production of PS under mild conditions by phospholipase D (PLD)-mediated transphosphatidylation. Toxic organic solvents were completely avoided throughout the process, from manufacturing to encapsulation. Results showed that higher enzyme selectivity and activity were found in the coconut oil-water and olive oil-water systems than in the traditional diethyl ether-water system. The maximum yields of PS in the two oil-water systems were more than 93%, whereas that in the diethyl ether-water system was only 78%. Hence, the coconut oil-water and olive oil-water systems should be the promising medium to produce PS and its microcapsules. Moreover, the enzymatic mechanism of PLD was simulated using molecular dynamics (MD) to understand diffusion channels, competitive bindings, solvent effects, structural changes, system stabilities, and product dissociation from the enzyme. MD results showed that more PLD-substrate complexes were detected in the oil-water systems than in the diethyl ether-water system. The conformational transition states of the protein between open and closed conformations were directly affected by the solvents used, and structural changes were observed in loop I (Asp309-Thr336). PLD in oil-water systems can not only maintain the native structure but also broaden the diffusion channels for substrates, which contributes to a higher enzymatic activity.